CASCADE-Cas3 enables highly efficient genome engineering in Streptomyces species

Area of Science:

• Microbiology
• Genetics
• Molecular Biology

Background:

• Type I CRISPR systems are prevalent in bacteria and archaea.
• Type I systems, unlike type II, utilize a multi-effector complex (CASCADE) and the processive nuclease Cas3 for DNA targeting and degradation.
• Cas3's processive nature and ability to create recombinogenic overhangs suggest potential for genome engineering.

Purpose of the Study:

• To develop and characterize a novel type I CRISPR-based genome engineering tool for Streptomyces.
• To evaluate the efficiency and capabilities of this new tool compared to existing systems like type II CRISPR-Cas9.
• To demonstrate the tool's utility in creating targeted and random deletions, as well as large genomic region substitutions.

Main Methods:

• Development of a plasmid system (pCRISPR-Cas3) utilizing a compact type I-C CRISPR system.
• Application of pCRISPR-Cas3 in various Streptomyces species for genome engineering.
• Comparative analysis of pCRISPR-Cas3 performance against pCRISPR-Cas9.

Main Results:

• The pCRISPR-Cas3 system demonstrated highly efficient genome engineering in Streptomyces.
• It enabled targeted and random-sized deletions with greater efficacy than pCRISPR-Cas9.
• The tool successfully performed substitutions of large genomic regions, including biosynthetic gene clusters, without further modifications.

Conclusions:

• The developed type I CRISPR-Cas3 system, pCRISPR-Cas3, is a powerful and efficient tool for Streptomyces genome engineering.
• It offers advantages over existing CRISPR-Cas9 systems for creating deletions and large-scale genomic modifications.
• pCRISPR-Cas3 shows broad applicability across multiple Streptomyces species.